1. Field of the Invention
The present invention relates to optical disk devices for a compact disk (CD) and a digital video disk (DVD), etc. wherein an optical disk capable of either writing once or rewriting many times information by irradiating a laser light thereon is used and an optical disk recording and reproducing method.
2. Description of the Related Art
Semiconductor laser noises are caused by the light reflected from a recording medium when a semiconductor laser is used as a light source for an optical disk drive. As a method of reducing semiconductor laser noises, a method wherein the high-frequency alternating current from a high-frequency current drive circuit is superimposed on the direct current, the superimposed current of which is fed to a semiconductor laser is known.
Conventionally, the semiconductor laser high-frequency superimposition method was carried out when primarily reading the low output laser power information. For example, disclosed in the Japanese Patent laid-open Application No. 5-197994 are a semiconductor noise reduction circuit and optical disk device which are capable of providing stable light sources to the fluctuation of the returned light volume by increasing the high-frequency superimposing volume via a high-frequency superimposing circuit when performing a focus-control by a focus servo system. Also, disclosed in the Japanese Patent laid-open Application No. 3-25732 is a semiconductor laser noise reduction circuit which prevents a current drive circuit from being heated by the amplitude of the high-frequency altering current to be superimposed on the direct current responsive to the detection of errors caused by the increase of noises generated when reproducing information.
Further, disclosed in the Japanese Patent laid-open Application No. 3-97130 is a semiconductor noise reduction circuit wherein noises are reduced by changing the gain from a gain changing amplifier and controlling the superimposed volume of the high-frequency current to be superimposed on the direct current, resulting in providing the modulation suitable for the superimposition thereof. in addition, disclosed in the Japanese Patent laid-open Application No. 4-6635 is an optical information recording and reproducing device wherein noises to be returned to a semiconductor laser are adequately reduced by changing and controlling the laser light pulse lighting frequency so that the returned light noise may be equal to or less than the standard volume. Furthermore, disclosed in the Japanese patent laid-open Application No. 6-52569 is a laser noise reduction device wherein noises can be reduced without causing any effect to the reproduced information signal even if the frequency of the superimposed signal to be fed to a laser diode is low so that the laser diode may be oscillated in a multimode.
The conventional semiconductor laser high-frequency superimposition as described above is a technology wherein amplitude of the high-frequency superimposed current is changed in response to the focus control drawing or the track crossing thereafter or error signals at time of the information reproduction or laser differential quantum efficiency, and the high-frequency superimposed current frequency is changed by the noise volume or clock signals. However, the superimposition technology as described above was not taken into account the time when the information was read or erased by using high power output since the foregoing changes were only made by the low output power at time of information reproduction. This has raised a problem that it is impossible to reduce noises generated at time of recording and erasing information and optimize the laser power to improve the S/N ratio at each operation mode.
It is, therefore, an object of the present invention to provide a semiconductor laser drive device capable of optimizing the laser power output at each operation mode of an optical disk device, an optical head, an optical disk device and a method of recording and reproducing information using an optical disk.